194 THE ELEMENTS OF VEGETABLE HISTOLOGY 



Corolla Tissues. The petals or corolla divisions 

 constitute the circle of floral leaves next inside the 

 calyx. If there be but one circle of floral leaves in 

 the flower it is classed as calyx, no matter what its 

 color or form. The corolla in most flowers is white 

 or variously colored, the color being due to pigments 

 contained in the parenchyma cells or dissolved in the 

 liquids within and around the cells. The histological 

 elements present in petals include epidermal tissues, 

 parenchyma and traces of fibro-vascular bundles. 

 The epidermis (Plate 64), is rather similar to that of 

 the leaf, rarely shows stomata and often possesses 

 papillae. Striated and beaded forms of cell walls 

 occur in this tissue, and glandular hairs are occasionally 

 present. The parenchyma corresponds to the meso- 

 phyll of leaves, but contains pigments or colored cell 

 liquids other than chlorophyll. The fibro-vascular 

 tissues are even more rudimentary than those of the 

 calyx, and consist of annular, spiral or reticulate vessels 

 almost lacking in fibrous supporting elements. 



Stamen Tissues. The stamens collectively con- 

 stitute the androecium or male reproductive structures 

 of the flower. Each stamen consists of anther, con- 

 nective and filament. The anther consists of two parts 

 attached to each other, and to the stem-like structure 

 or filament, by the connective. The histological 

 elements present in stamens include epidermal tissues, 

 parenchyma, fibro-vascular tissues and pollen grains. 

 The epidermis covering the anther and filament is 

 similar to that of the corolla. Parenchyma is present 

 in the filament and connective, but is wanting or much 

 reduced in the anther. The parenchyma cells (Plate 

 64), are small and are disposed around the simple, 



